The planet Jupiter. 318
times bigger than the Earth, with a few dozen moons going around
it. The planet Jupiter is visible from Earth just by looking at
the sky at the right time. It looks like a bright star.

Four of the moon of
Jupiter can be seen through binoculars. If you see something in
the sky looking like a bright star and try looking at it through
binoculars, the sights of these four moons is more amazing than
you might guess if you've never tried this. [More
about this]

The atmosphere of Jupiter
is a turbulent sea of storms and there's not really a solid
surface. It's possible to create effects which look a bit like
the goings-on in the Jovian atmosphere by making tea in a pint
glass with the right amounts of sugar and milk. Different layers
of concentration and temperature cause circulating whirlpools at
transition layers.

More radio energy comes
off the planet than arrives. Though it's tempting to think this
might be alien life-forms with radio transmitters, it's most
likely to be instead that the planet is so big that it is part-way
to being a star (a substellar object) and the atomic reactions
going on inside the planet cause emission of radiation.

Because of the large
gravity of the planet, it has the reputation of being the vacuum-cleaner
of the solar system and tends to attract asteroids that are about.
However, some people blame the planet for various gravity snooker-shots
which deflect asteroids all over the place.

A few years ago a large
object called Shoemaker-Levy9 collided with the planet Jupiter.
If it had hit the planet Earth instead it would have been the End
of the World. See Asteroids Colliding with the Earth

The moons of Jupiter are
many, and there seem to be more of them being discovered all the
time. The four largest: Ganymede, Callisto, Europa, and Io, are
all quite different from each other, as revealed by a NASA space mission, which got a closer
look than Galileo, who was first to discover the four largest
moons. (That's why they're known as The Galilean Moons of Jupiter).